Preparations for Historic US - North Korea Summit in the Fast Lane

White House top brass say they're "actively preparing" for the upcoming Singapore summit between President Donald Trump and North Korean leader Kim Jong Un.

An advance team is in Singapore, including Secretary of Defense James Mattis, is finalizing preparations.

In the Korean Demilitarized Zone, the US ambassador's delegation continues diplomatic negotiations with the North Korean delegation.

"Discussions have been very positive, and significant progress has been made," White House Press Secretary Sarah Sanders said Monday. "I can tell you the president has been receiving daily briefings on North Korea from his national security team."

The schedule calls for Trump and Kim to meet for the first time Tuesday, June 12 at 9 am Singapore time, which is 9 pm Monday night Washington, DC time.

Is There a National Security Riff in the White House?

Meanwhile, the White House is denying any rift between National Security Advisor John Bolton and Secretary of State Mike Pompeo, despite reports from other national news organizations.

CNN is reporting Pompeo angrily confronted Bolton in a heated conversation at the White House.

"There has been considerable tension between them ever since," a person familiar with the West Wing confrontation told CNN.

Other news organizations are reporting that Bolton has been kept out of the process after his remarks about the "Libyan model" almost stopped the meeting before it started.

The Libyan leader Muammar Gaddafi was killed by rebels in 2011 during a conflict in which the US intervened a few years after Libya dismantled its nuclear program.

North Korea responded shortly afterward by lashing out at Bolton, saying it could not hide its anger toward him.

Now, Pompeo has told Trump that allowing Bolton to meet with North Korean officials would be "counterproductive," according to CNN.